JPH03217227A - Membrane reactor for dehydrogenation reaction - Google Patents

Abstract

PURPOSE:To increase conversion efficiency at a temp. lower than that of the conventional process by forming a Pd-contg. thin film having <=50mum thickness on one surface of a porous metallic body as the hydrogen separation membrane and forming the membrane reactor for dehydrogenation reaction with the membrane. CONSTITUTION:A dehydrogenation catalyst 3 is packed between the outer tube 1 of a reaction tube and a hydrogen separation membrane 2 and held by a catalyst supporting plate 7. The raw gas is supplied to the catalyst bed 3 from an inlet 4, hence the dehydrogenation reaction proceeds, and the generated hydrogen is permeated through the membrane 2 and discharged from a hydrogen outlet 6. The membrane 2 is formed by laminating a Pd-contg. thin film having <=0.5mu thickness at least on one surface of the metallic body having 0.1-2.0mu pores. The plural membranes 2 are set in the reaction tube 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reactor used for dehydrogenation reaction, and more specifically, a hydrogen separation membrane is installed in the reaction tube to exclude a part of the hydrogen of the reaction product. This invention relates to a membrane reactor that allows a dehydrogenation reaction to occur.

[Conventional technology]

The dehydrogenation reaction that produces hydrogen is generally expressed as follows.

Cr, H. → CnL-2+ L
(t)CnH+a+nLO →
ncO + (n+ m/2)Hz (
2) CnL + 2nH20- ncO2+ (2
n+m/2)Hz (3) The above reaction is a reaction accompanied by a large endotherm, and in order to increase the conversion rate above thermodynamic equilibrium, it is necessary to raise the temperature to a high temperature, and it is usually carried out at a high temperature of 600° C. or higher.

Table 1 of Shimokita shows the reaction temperatures required to obtain each equilibrium conversion rate in the hydrocarbon dehydrogenation reaction of reaction (1) above.

Further, as a representative example of the above reactions (2) and (3), the equilibrium conversion rates in the steam reforming reaction of methane are shown in Table 2 below.

Table 2 Equilibrium conversion rate in methane steam reforming reaction (LD/CH4 = 3 mol/mol) In addition, porous glass,
It has been proposed to use a membrane reactor in which a hydrogen separation membrane such as palladium-plated porous glass is installed inside the reactor, and a portion of the hydrogen produced by the reaction is taken out of the reactor while the dehydrogenation reaction takes place. .

[Problem to be solved by the invention]

As previously mentioned, conventional dehydrogenation reactions require very high temperatures to achieve a given conversion. Therefore, it is necessary to use high-grade materials that can be used even at high temperatures. In addition, because the conversion rate is low, the reactor outlet gas is cooled to separate the raw material and the reaction product, and the raw material is recycled for use, but a recycling gas compressor is required, and heating and cooling are required. Because it is repeated, there are problems such as low thermal efficiency. Furthermore, since the reaction temperature is high, there is a problem in that there are many side reactions and the activity of the catalyst is greatly reduced.

Furthermore, membrane reactors using porous glass or palladium-plated porous glass have low strength and are difficult to manufacture into pipes with a length of 50 cm or more, which poses practical problems.

[Means to solve the problem]

The present invention includes a reactor having a raw material supply port and a product discharge port, the inside of which is filled with a catalyst, and the outside of which is equipped with a heating means. A dehydrogenation reaction characterized by comprising a hydrogen removal means constituted by a hydrogen separation membrane in which a Pd-containing thin film with a thickness of 50μ or less is formed on at least one surface of a porous metal body having pores of 1 to 20μ. It is a membrane reactor for

That is, the present invention was made to solve the above-mentioned problems, and includes a thin film containing Pd with a thickness of 50 μm or less on at least one surface of a porous metal body having pores of 0.1 to 20 μm. This is a membrane reactor in which a hydrogen separation membrane formed with hydrogen is installed in the reactor, and a dehydrogenation reaction is carried out while excluding a part of the hydrogen of the reaction product.

In the present invention, the porous metal having pores includes 3
A porous metal body that has heat resistance that can withstand temperatures of 00°C or higher, has no reactivity with the gas to be treated, and has pores as uniform as possible within the range of 0.1 to 10μ. It is appropriate to use. The reason why the pore diameter is set to 0.1μ or more is to prevent gas diffusion from being obstructed.
The reason why the thickness is set to 0μ or less is that pinholes are likely to occur when a thin film containing Pd is coated to a thickness of 50μ or less. Note that it is appropriate to use a cylindrical or plate-shaped porous metal body, and preferably one having a thickness of 0.2 to 2 mm from the viewpoint of strength as a support and workability.

Examples of porous metal bodies in the present invention include the following.

(1) Foamed (porous) metal is press-molded to control the pore diameter, and the pores are further made smaller by thermal spraying or plating.

(2) Molded metal fine powder with small particle size (50μ or less).

(3) Powder that can be removed by chemical reaction (for example, graphite that can be removed by combustion) is mixed with metal powder or added to molten metal, and then the powder is removed by chemical reaction to generate pores.

(4) Metal fiber.

In the present invention, the thin film containing Pct is Pd
It is suitably made of an alloy containing 100% Pd or 10% by weight or more of Pd, and has a film thickness of 50 μm or less, particularly 2 to 20 μm. As an alloy containing 10% by weight or more of Pd, P
Refers to those containing, in addition to d, group Ⅰ elements such as Pt, Rh, Ru, and Ir, and group Ib elements such as Cu, Ag, and Au.

As an example of a method for forming a Pd-containing thin film having a thickness of 50 μm or less on at least one surface of a porous metal body, the following method is used.

(1) After liquid-phase surface activation treatment such as plating (immersion alternately in an aqueous solution of tin chloride and palladium chloride), electroless plating (immersion in a solution containing a palladium compound and a reducing sword), and , electroplated after electroless plating.

(2) Gas phase methods such as vacuum evaporation, ion plating, and vapor phase chemical reaction (CVD).

A porous metal body on which a thin film of Pal or Pd alloy is formed as described above can be used as a hydrogen separation membrane that selectively permeates only hydrogen.

[Effect]

A membrane reactor in which a hydrogen separation membrane having a Pd-containing thin film prepared as described above is installed in a reaction tube has the following effects.

(1) By simultaneously carrying out the reaction while removing hydrogen, which is a part of the reaction product, from inside the reaction tube, the reaction can proceed without being constrained by thermodynamic equilibrium. That is, a conversion rate higher than the equilibrium conversion rate can be obtained.

This effect allows the reaction temperature to be lower than in conventional methods.

(2) By using a porous metal membrane, it can be installed in a reaction tube without problems with strength, workability, etc.

The outline of the apparatus for carrying out the method of the present invention will be explained below.

FIG. 1 is a schematic diagram of the main parts of an apparatus for carrying out the method of the present invention.
1 is a reaction tube (outer tube), 2 is a hydrogen separation membrane, 3 is a catalyst layer, 4
5 is a raw material gas inlet, 5 is a generated gas outlet, 6 is a hydrogen outlet, and 7 is a catalyst support plate.

A dehydrogenation reaction catalyst 3 is filled between the outer tube 1 of the reaction tube and the hydrogen separation membrane 2, and is held on a catalyst support plate 7. A raw material gas is supplied to the catalyst layer 3 through an inlet 4, and the dehydrogenation reaction proceeds. As the reaction progresses, generated hydrogen passes through the hydrogen separation membrane 2 and is discharged from the hydrogen outlet 6. The unreacted gas and the produced gas pass through the catalyst support plate 7, which is made of a perforated plate so that the gas can easily pass therethrough, and are discharged from the produced gas outlet 5.

Heat is supplied from the outside of the outer tube 1 of the reaction tube to maintain the reaction temperature and supplement the heat necessary for the reaction. Hydrogen separation membrane 2
A plurality of are installed in the reaction tube 1. Furthermore, inert gas (sweep gas) can be passed through the hydrogen separation membrane 2 in order to increase the hydrogen permeation rate.

[Example 1] Using fine SUS 304 metal powder with an average particle size of 1μ,
Porous metal pipe with an average pore diameter of 0.5μ (10°”
Sample 1, in which only palladium was deposited on the outer surface of the vibrator, was an alloy of palladium and silver (Pd:Ag=85:15 weight ratio).
Sample 2 was also deposited with palladium and copper alloy (Pd
:Cu=90:10 weight ratio) was prepared.

Porous metal pipes coated with palladium or palladium alloy (samples 1 to 3) were used as hydrogen separation membranes, and tests were conducted using the apparatus shown in FIG. 2. Hydrogen separation membrane 1
1 to the stainless steel outer tube l3 with an O ring 12,
The outside is heated in an electric furnace. Temperature is thermocouple 1
8 was used to measure the center of the inner tube. The catalyst was filled in the space 19 between the outer tube 13 and the hydrogen separation membrane 11, which is the inner tube.

After filling the catalyst with the composition of Ni020wt% and Al2a380wt% (average particle size 1mm>5g, 500wt%
Hydrogen reduction was carried out at ℃.

A mixed gas of methane and water vapor was continuously supplied from the supply hole 14, and generated gas other than permeated hydrogen was discharged from the discharge hole 15. Further, argon was supplied as a sweep gas from the upper supply hole 17, and a hydrogen-containing gas was obtained from the take-out hole 16 together with the hydrogen that had permeated through 1 liter of the hydrogen separation membrane.

The reaction conditions are as follows.

The test results are shown in Table 2.

Table 2 [Comparative Example 1] A methane reforming reaction experiment was conducted in the same manner as in Example 1, except that a hydrogen separation membrane was not used (no sweep gas was flowed), and the methane conversion rate was 24%. .

[Example 2] In the test using the porous metal pipe (sample 3) in Example 1, the reaction pressure and temperature were changed and the results were as follows.

[Example 3] Porous metal pipe with an average pore diameter of 2μ (laminated sintered wire mesh filter manufactured by Nichidai ■: 10°D x 8 20X500
After electroless plating using L[[lffl], electroplating was performed to coat with 20μ of Pd, and a dehydrogenation reaction of propane, butane and ethylbenzene was performed using the same apparatus and method as in Example 1.

Common reaction conditions are as follows.

Test results 11 are as shown in Table 3.

Table 3 [Comparative Example 2] Table 4 shows the results of a dehydrogenation reaction of propane, butane, and ethylbenzene performed in the same manner as in Example 3, except that a hydrogen separation membrane was not used (no sweep gas was flowed).

Table 4 [Effects of the Invention] In the dehydrogenation reaction of the present invention, a hydrogen separation membrane in which a thin film containing Pd is formed on a porous metal body is installed in a reaction tube, and a part of the hydrogen in the reaction product is removed by the reaction. By excluding it from the system, a high conversion rate could be obtained at a lower temperature than in the conventional method.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the outline of an apparatus for carrying out the method of the present invention, and FIG. 2 is a schematic diagram of a test reaction apparatus used in an example of the method of the present invention. Rut・1 diagram

Claims (1)

[Claims] A reactor having a raw material supply inlet and a product outlet, filled with a catalyst inside and equipped with heating means on the outside, and having pores of 0.1 to 20μ provided in the catalyst packed bed of the reactor. 1. A membrane reactor for dehydrogenation reaction comprising a hydrogen removal means constituted by a hydrogen separation membrane in which a Pd-containing thin film with a thickness of 50 μm or less is formed on at least one surface of a porous metal body.